CBT Training Trends
Larry Adams takes a look at today's trend towards computer-based learning technologies and the potential savings it produces in the April 2000, Quality Online E-zine
To read more about it, Click here

GD&T Professional Certification Available
ASME has established a certification program for GD&T Professionals. The GDTP Certification Program provides the means to recognize proficiency in the understanding and application of GD&T principles. Click here

ASME Standards Info
Keep up to date with issues pertaining to the ASME standards, with Mechanical Engineering Online.
Click here

GD&T Instructor's Kit Goes Digital
ETI launches its new Digital Instructor's Kit--all the course materials an instructor needs to teach an entire GD&T course included on one handy CD-ROM.
To read more about it, Click here
To download a demo, Click here

ETI Offers On-Site Training 
Find out more about what ETI has to offer your organization. Click here

Tech Calendar

ETI Tech Calendar Now On Website
Stay up to date on the latest industry news with the ETI Tech Calendar.

President
Alex Krulikowski

Office Manager
Donna Pokrywki

Product Development
Jamy Krulikowski

Programming
Cindi Rowe
Jim Todd
Nathaniel Kraft

Sales 
Kathy Darfler
Nancy Davis

Website/Internet Svcs.
Brandon Billings

Artist/Network Admin.
Matthew Pride

Writer/Editor
Katherine Palmer

Order Processing
Tina White

Shipping
Gary Walls

Receptionist
Lindsay Carlington

Eliminating the Confusion:
The Nine Rules for Composite Position Tolerancing 

The Pattern Rule
A composite position control must be applied to a set of multiples features of size (i.e. a pattern of holes, coaxial diameters, etc.).

The Segment Rule
A composite position control can only contain two segments (the PLTZF and the FRTZF).

The Upper Segment Rule
The upper segment can and must control the location and/or orientation of the pattern.

The Lower Segment Rule
The lower segment can and must only control the spacing and/or orientation of the pattern.

The Tolerance Refinement Rule
The tolerance value of the lower segment must always be a refinement of the tolerance value of the upper segment.

The Basic Dimension Rule
Basic dimensions (specified or derived) that define location of toleranced features apply to the upper segment only. Basic dimensions (specified or derived) that define spacing and/or orientation apply to both segments.

The Datum References Rule
Any datum references and datum modifiers in the lower segment must be repeats and in the same order of the datum references and datum modifiers of the upper segment.

The Segment Verification Rule
Each segment of a composite position control must be verified separately.

The Separate Requirement Rule 
The simultaneous requirement default does not apply to the lower segment of composite position controls.
 

In the next issue of ETImail: The Nine Myths of GD&T

Standards in the News

Standards are important to keep our lives safe and functional. When they're not met, we end up fixing errors, repairing problems, and righting wrongs--even putting our lives in jeopardy.

ETImail takes a look at real-life issues where standards have failed or need improvement. This month: the Mars Climate Orbiter fiasco. 

MARS CLIMATE ORBITER TEAM FINDS LIKELY CAUSE OF LOSS
When the Mars Climate Orbiter project failed in 1999, NASA's Jet Propulsion Laboratory internal peer review team went to work to discover the problem. Their preliminary findings indicated that, "A failure to recognize and correct an error in a transfer of information between the Mars Climate Orbiter spacecraft team in Colorado and the mission navigation team in California led to the loss of the spacecraft last week." 

"People sometimes make errors," said Dr. Edward Weiler, NASA's Associate Administrator for Space Science. "The problem here was not the error, it was the failure of NASA's systems engineering, and the checks and balances in our processes to detect the error. That's why we lost the spacecraft." 

"Our inability to recognize and correct this simple error has had major implications," said Dr. Edward Stone, director of the Jet Propulsion Laboratory. "We have underway a thorough investigation to understand this issue." 

The project failed at a cost of hundreds of millions of dollars. Here's the breakdown:

PROJECT COST  $327.6 million total for both orbiter and lander (not including Deep Space 2) $193.1 million for spacecraft development $91.7 million for launch $42.8 million for mission operations Full Details

THE REST OF THE STORY. . . 
This expensive mistake had an unbelievably simple cause--a failure to make certain which standard of measurement was being used: one team was using the metric system, while the other was using English units of measure. Here's a quote from the peer review report: "Findings indicate that one team used English units (e.g., inches, feet and pounds) while the other used metric units for a key spacecraft operation. This information was critical to the maneuvers required to place the spacecraft in the proper Mars orbit." Full Story
 

Mars Climate Orbiter and its sister mission, the Mars Polar Lander, are part of a series of missions in a long-term program of Mars exploration managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. JPL's industrial partner is Lockheed Martin Astronautics, Denver, CO. JPL is a division of the California Institute of Technology, Pasadena, CA. More Info

 

The ETI Mailbag

I would like information on "simultaneous requirement default." Is this subject covered in Y14.5 or in any of your materials?

Information on "Simultaneous Requirement Default" is in sections 5.3.6.1 and 5.3.6.2 of the Y14.5 dimensioning and tolerancing standard. It is also covered in Chapter 18 of the Advanced Concepts of GD&T textbook.

The USCAR Y14.5 addendum is a little bit tricky to find. I will tell you where to go to get the GM version of the USCAR addendum, but I'm not sure where the Ford and Chrysler versions are located. The GM version is located on the following website: www.gmsupplypower.com -- click the "Search Tool" link on the right hand side and it will take you to the search page. Type in "dimensioning and tolerancing addendum" in the search window. It will take you to a page listing all the different addendums. The one you are looking for is probably the first entry called GM Global Dimensioning and Tolerancing Addendum, 2001. It is a free download in ZIP format, and the addendum is in a Microsoft Word format.
 

Send your GD&T questions to etimailbag@etinews.com.

 

We would appreciate it if you'd keep us in mind when you need GD&T training, consulting, or GD&T products. Feel free to contact us by email or by phone at 734-728-0909 or 800-886-0909. To subscribe to ETImail, click here. To contact us with questions, comments, or story ideas, click here.  To unsubscribe from ETImail, click here. The contents of this newsletter may not be reproduced in any form without express permission from Effective Training Inc. Copyright © 2003 Effective Training Inc. All rights reserved.